Nitrogen fixation light

The absorption of light by semiconductors cremes electron-hole pairs e h+) which can be separated because their components diffuse in different directions. The energies of these moieties can be stored by several mechanisms or used in photocatalysis or photosynthesis for nitrogen fixation, formation of amino acids, methanol, etc. The efficiencies of such conversions depend almost entirely upon the semiconductor material, and as yet these efficiencies are too low for significant application. Currently the most promise is demonstrated by the use of titania on a platinum substrate or single crystals of strontium titanate. See also Photoelectric Effect. 

Table 1 summarizes several redox transformations that can be accomplished in artificial photosynthetic assemblies including the photolysis of water, carbon dioxide reduction, and nitrogen fixation processes. The endoergicities of these transformations, and the number of electrons involved in the reduction processes, are also indicated in the table. It is evident that the energy per electron to drive the various transformations are met by visible light quanta. 

The studies discussed so far deal - for good reasons - with the isolated FeMoco. However, qualitative molecular modeling has also been used to identify possible proton transfer routes from the surface of the nitrogenase protein to the FeMoco (40) and mechanistic aspects of biological nitrogen fixation are discussed in the light of such data (10-12). 

N. Rigopoulos, and R. C. Fuller The pyruvate phosphoclastic reaction and light-dependent nitrogen fixation in bacterial photosynthesis. Proc. Nat. Acad. Sci. (U. S.) 52, 762-768 (1964). 

Breitbarth, E., Wohlers, J., Klas, J., Roche, J. L., and Peeken, I. Nitrogen fixation and growth rates of Trichodesmium IMS-101 as a function of light intensity. Mar. Ecol. Prog. Ser., submitted. 

Kiipper, H., Ferimazova, N., Sedik, 1., and Berman-Frank, 1. (2004). Traffic lights in Trichodesmium. Regulation of photosynthesis for nitrogen fixation studied by chlorophyU fluorescence kinetic microscopy. Plant Physiol. 135, 2120—2133. ... 

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